/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance
 * with the License.  You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing,
 * software distributed under the License is distributed on an
 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
 * KIND, either express or implied.  See the License for the
 * specific language governing permissions and limitations
 * under the License.
 */
package org.apache.iotdb.hadoop.tsfile;

import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.fs.FileSystem;
import org.apache.hadoop.fs.Path;
import org.apache.hadoop.io.DoubleWritable;
import org.apache.hadoop.io.MapWritable;
import org.apache.hadoop.io.NullWritable;
import org.apache.hadoop.io.Text;
import org.apache.hadoop.mapreduce.Job;
import org.apache.hadoop.mapreduce.Mapper;
import org.apache.hadoop.mapreduce.Reducer;

import java.io.IOException;

/**
 * One example for reading TsFile with MapReduce. This MR Job is used to get the result of
 * sum("device_1.sensor_3") in the tsfile. The source of tsfile can be generated by <code>
 * TsFileHelper</code>.
 */
public class TSFMRReadExample {

    public static void main(String[] args)
            throws IOException, ClassNotFoundException, TSFHadoopException {

        if (args.length != 3) {
            System.out.println("Please give hdfs url, input path, output path");
            return;
        }
        Path inputPath = new Path(args[1]);
        Path outputPath = new Path(args[2]);

        Configuration configuration = new Configuration();
        // set file system configuration
        // configuration.set("fs.defaultFS", HDFSURL);
        Job job = Job.getInstance(configuration);

        FileSystem fs = FileSystem.get(configuration);
        if (fs.exists(outputPath)) {
            fs.delete(outputPath, true);
        }

        job.setJobName("TsFile read jar");
        job.setJarByClass(TSFMRReadExample.class);
        // set mapper and reducer
        job.setMapperClass(TSMapper.class);
        job.setReducerClass(TSReducer.class);
        // set inputformat and outputformat
        job.setInputFormatClass(TSFInputFormat.class);
        // set mapper output key and value
        job.setMapOutputKeyClass(Text.class);
        job.setMapOutputValueClass(DoubleWritable.class);
        // set reducer output key and value
        job.setOutputKeyClass(Text.class);
        job.setOutputValueClass(DoubleWritable.class);
        // set input file path
        TSFInputFormat.setInputPaths(job, inputPath);
        // set output file path
        TSFOutputFormat.setOutputPath(job, outputPath);

        /** special configuration for reading tsfile with TSFInputFormat */
        TSFInputFormat.setReadTime(job, true); // configure reading time enable
        TSFInputFormat.setReadDeviceId(job, true); // configure reading deltaObjectId enable
        String[] deviceIds = {"device_1"}; // configure reading which deviceIds
        TSFInputFormat.setReadDeviceIds(job, deviceIds);
        String[] measurementIds = {
                "sensor_1", "sensor_2", "sensor_3"
        }; // configure reading which measurementIds
        TSFInputFormat.setReadMeasurementIds(job, measurementIds);
        boolean isSuccess = false;
        try {
            isSuccess = job.waitForCompletion(true);
        } catch (InterruptedException e) {
            Thread.currentThread().interrupt();
            throw new IOException(e.getMessage());
        }
        if (isSuccess) {
            System.out.println("Execute successfully");
        } else {
            System.out.println("Execute unsuccessfully");
        }
    }

    public static class TSMapper extends Mapper<NullWritable, MapWritable, Text, DoubleWritable> {

        @Override
        protected void map(
                NullWritable key,
                MapWritable value,
                Mapper<NullWritable, MapWritable, Text, DoubleWritable>.Context context)
                throws IOException, InterruptedException {

            Text deltaObjectId = (Text) value.get(new Text("device_id"));
            context.write(deltaObjectId, (DoubleWritable) value.get(new Text("sensor_3")));
        }
    }

    public static class TSReducer extends Reducer<Text, DoubleWritable, Text, DoubleWritable> {

        @Override
        protected void reduce(
                Text key,
                Iterable<DoubleWritable> values,
                Reducer<Text, DoubleWritable, Text, DoubleWritable>.Context context)
                throws IOException, InterruptedException {

            double sum = 0;
            for (DoubleWritable value : values) {
                sum = sum + value.get();
            }
            context.write(key, new DoubleWritable(sum));
        }
    }
}
